When semiconductor chip packages are applied to a substrate, it is convenient for the packages to be arranged on one side of the substrate and the wiring between the packages to be arranged on the other side. In order to accomplish this, it is necessary to utilize an arrangement known as a via. This consists of a hole through the substrate extending from one surface to the other. The walls of the hole are coated with an electrically conductive material, such as by plating. An electrically conductive pad is formed on each surface which is in electrical contact with the via. In standard vias, on the surface which receives the packages, the via pads are connected by a surface conductor to another pad which is nearby. This pad is used to receive a contact connected to the package. One common package contact is a ball grid array (BGA). Balls of solder are applied to the bottom of the package in a pattern which matches the contact pads on the substrate. Solder paste is applied to the contact pads and the assembly is heated to reflow the solder and to connect the package to the substrate.
While this arrangement is widely used, this arrangement with two pads and a surface conductor for each package contact uses a lot of surface area and makes routing of connections difficult. Another arrangement has been suggested whereby a single pad is used both as a via pad and a contact pad. This arrangement, known as via in pad (VIP), allows for easier routing on the substrate surface. However there have been manufacturing difficulties in that the solder balls often do not form a strong connection with the pad.